Querying Knowledge Graphs on the Web with Comunica

Knowledge Graphs on the Web
are a multifaceted story

• Publication APIs
• Access patterns
• Query languages
• ...

Difficulties for app developers

• Distinguishing APIs

  What kind of API is this?

• Interacting with APIs

  How to efficiently get data from this API?

• Combining APIs

  How to combine data across different APIs?

Abstract access to Knowledge Graphs

Hide the complexities of reading and writing for app developers

↔ ↔

Image credit

Queries as abstraction layer

• Say what needs to happen, not how

  Declarative queries hide complexities of data retrieval

• Queries are reusable

  Queries are not API-specific

• Execution via a generic, reusable query engine

  Abstracts away complexities for executing queries
  New optimisations can be used by merely updating query engine

Heterogeneity and Federation

• Understanding any source

  Give it any URL, and Comunica will aim to query it as efficient as possible
  Linked Data documents, Triple Pattern Fragments, SPARQL endpoints, ...

• Combining multiple sources

  Data can be spread over multiple sources

• Future: source discovery

  All relevant sources may not always be known beforehand
  For fully decentralised data (Solid)

Flexible and Modular Meta-Query Engine

• Collection of building blocks

  160+ independent modules implement specific functionality

• Combining building blocks

  Building custom query engines with specific functionality and settings
  Using a flexible configuration system
  Presets: Comunica SPARQL, Comunica Solid, ...

Comunica is Open

• Open standards

  Implements Web standards (SPARQL, RDF, ...)
  Implemented using Web standards (JavaScript)
  Interoperable with other TS/JS libraries using the RDF/JS interfaces

• Open source

  MIT-licensed: https://github.com/comunica/comunica

• Open governance

  Comunica Association connects organisations
  

Query in the browser

• https://query.linkeddatafragments.org/

  Client-side querying of sources using SPARQL or GraphQL

Query on the command line

• Installing Comunica SPARQL globally

  $ npm install -g @comunica/query-sparql

• Running a SELECT query

  $ comunica-sparql https://fragments.dbpedia.org/2016-04/en \
      "SELECT * WHERE { ?s ?p ?o } LIMIT 100"

• Running a CONSTRUCT query

  $ comunica-sparql https://fragments.dbpedia.org/2016-04/en \
      "CONSTRUCT WHERE { ?s ?p ?o } LIMIT 100"

Query in an JavaScript/TypeScript app

• Installing Comunica SPARQL locally

  $ npm install @comunica/query-sparql

• Creating a new engine

  const myEngine = new QueryEngine();

• Running a SELECT query

  myEngine.queryBindings(`SELECT...`, { sources: [ 'http...' ]});

More on https://comunica.dev/docs/

• Getting started guides

  Tutorials on how to use Comunica in different ways

• Modification guides

  Tutorials on how to modify and configure custom query engines

• Internal details

  In-depth documentation on the internals and architecture

The Comunica Association

• A non-profit for the sustainability of Comunica

  Open to anyone

• Receives funding from members and sponsors

  Pays developers for bugs and features on the roadmap
  Members collectively determine the long-term roadmap

• Management of bounties

  Companies place bounties on bugs/features, claimed by developers

Bounty program

Members and sponsors

Comunica abstracts access
to Knowledge Graphs

• Via declarative queries

  SPARQL, GraphQL, ...

• Runs anywhere

  CLI, client-side (browsers), server-side (Node.js), ...

• Open

  Anyone can use it and contribute